RBS (Rutherford BackScattering) Y (a,a) Y

This method of analysis is based on the detection of the charged particles elasticaly scattered by the nuclei of the analyzed sample. It allows to separate the atomic masses of the elements and to determine the profile distribution in function ot the detected energy.

The cinematic is relatively simple and the energy is given by:

where:

So, for a given angle and a given incident particle, the energy of the scattered particle mostly depends on the nucleus mass, at the condition that the reaction takes place near the surface where the energy lost of the incident beam is negligible in regard of E0.

When M0 << M1, K increases with M2 to attain 1, which allows the mass separation of target nuclei. The mass resolution also depends on E0, and alpha particles with energy near 2 MeV are generally used.

The characteristics of the method are the following:

• The differential cross section of elastic diffusion is well known and it allows to calculate the absolute concentrations without standards. It is given by

where

• It is possible to deconvoluate the spectrum of the particles scattered by a thick target composed of several layers of elements and to determine their nature and their thickness.

The following figure shows the different cases that can arise in function of atomic masses present in the successive layers.

This picture shows a spectrum obtained when bombarding a double layer of Hafnium and Yttrium on a thick Silicium substrate.

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